PECAM1 Antibody

What is PECAM1/CD31 and why is it significant in vascular research?

PECAM1 (CD31) is a 130-140 kDa transmembrane glycoprotein that belongs to the immunoglobulin superfamily. It plays crucial roles in vascular biology by mediating cell-cell adhesion, regulating leukocyte transmigration, participating in angiogenesis, and maintaining endothelial cell barrier function. The significance of PECAM1 in research stems from its predominant expression on endothelial cells, platelets, and certain leukocyte subpopulations, making it an excellent marker for endothelial cells and vascular structures . PECAM1 contains both extracellular and cytoplasmic domains, with the extracellular portion comprising six immunoglobulin-like domains that participate in homophilic and heterophilic interactions . The cytoplasmic domain contains sites for phosphorylation and protein-protein interactions that facilitate signaling functions. These structural features enable PECAM1 to serve as both an adhesion molecule and a signaling receptor, making it valuable for investigating multiple aspects of vascular biology.

How do I determine which PECAM1 antibody format is appropriate for my experimental system?

The selection of an appropriate PECAM1 antibody format depends on several experimental considerations, including the species being studied, the specific application, and the domain of interest. For cross-species studies, researchers should consider antibodies that recognize conserved epitopes across different species, such as the Human/Mouse/Rat CD31/PECAM-1 Antibody (AF3628) . When studying domain-specific functions, select antibodies that target specific regions, such as mAbs PECAM-1.3 (specific for IgD1), PECAM-1.2 (specific for IgD6), or mAb 235.1 (specific for the C-terminal 15 amino acids) .

For studies requiring minimal interference with PECAM1 function, consider using Fab fragments, which can be generated using immobilized papain and confirmed by SDS-PAGE to ensure no intact IgG remains . When signal amplification is critical, such as in tissues with low PECAM1 expression, full IgG antibodies may provide better sensitivity. For functional studies investigating PECAM1-mediated processes, domain-specific antibodies can help dissect the role of different PECAM1 regions in cellular functions like barrier regulation or migration .

What validation methods should I employ to confirm PECAM1 antibody specificity?

Rigorous validation of PECAM1 antibody specificity is essential for generating reliable research data. A multi-method approach should include:

• Western blot analysis using positive controls like endothelial cell lines (bEnd.3) and negative controls such as PECAM1-deficient cell lines .

• Flow cytometry comparative analysis of PECAM1-expressing cells (like splenocytes or granulocytes) versus control cells .

• Immunocytochemistry using PECAM1 knockout cell lines, such as the CD31/PECAM-1 knockout THP-1 human cell line, compared to wild-type cells .

• ELISA testing against purified PECAM1 antigen to confirm binding efficacy, particularly important for domain-specific antibodies .

• Cross-reactivity testing against related adhesion molecules to ensure selectivity for PECAM1.

A particularly robust validation approach is demonstrated by the CD31/PECAM-1 specificity testing in knockout cell lines, where the antibody shows clear membrane staining in wild-type cells but no detection in the knockout line . This methodological approach provides definitive evidence of antibody specificity and should be conducted before proceeding with experimental applications.

What are the optimal protocols for using PECAM1 antibodies in Western Blot analysis?

Successful Western blot analysis with PECAM1 antibodies requires careful optimization of several parameters. Based on data from validated protocols, researchers should consider the following methodology:

For optimal detection, probing membranes with 0.5-10 μg/mL of anti-PECAM1 antibody has proven effective, followed by appropriate HRP-conjugated secondary antibodies . When using the Human/Mouse/Rat CD31/PECAM-1 Antibody (AF3628), a concentration of 0.5 μg/mL has successfully detected PECAM1 in mouse endothelioma cell lines . For the Human CD31/PECAM-1 Antibody (AF806), 10 μg/mL effectively detected PECAM1 in human cell lines such as Jurkat and HepG2 .

The choice of detection system should be based on the expected expression level—standard ECL for high expression and more sensitive detection systems for lower expression levels. Additionally, researchers should include appropriate positive controls, such as endothelial cells or platelets, which naturally express high levels of PECAM1.

How should I optimize PECAM1 antibody applications in Flow Cytometry?

Flow cytometry with PECAM1 antibodies requires specific optimization strategies to ensure accurate detection and quantification. The methodology should incorporate:

First, determine the optimal antibody concentration through titration experiments—successful protocols have used the Human/Mouse/Rat CD31/PECAM-1 Antibody (AF3628) for detection in mouse and rat splenocytes and whole blood granulocytes . Sample preparation should preserve membrane integrity, as PECAM1 is primarily membrane-localized. For blood samples, red blood cell lysis should be performed carefully to avoid affecting PECAM1-expressing cells.

For staining protocols, include proper blocking steps to reduce non-specific binding, particularly when working with heterogeneous cell populations. Use fluorophore-conjugated secondary antibodies appropriate for your cytometer configuration—studies have successfully employed Allophycocyanin-conjugated Anti-Goat IgG Secondary Antibody (F0108) and Phycoerythrin-conjugated Anti-Goat IgG Secondary Antibody (F0107) .

Always include appropriate isotype controls, such as AB-108-C, to establish gating strategies and determine background staining levels . For multi-parameter analysis, consider the spectral overlap between fluorophores when designing panels that include PECAM1 antibodies. Following the protocol for Staining Membrane-associated Proteins provides optimal results for PECAM1 detection .

What are the critical factors for successful Immunohistochemistry with PECAM1 antibodies?

Immunohistochemistry (IHC) with PECAM1 antibodies requires attention to several critical factors to achieve specific staining of vascular structures. The following methodology has been validated for optimal results:

Tissue preparation significantly impacts staining quality—for paraffin-embedded sections, heat-induced epitope retrieval using basic retrieval reagents (such as VisUCyte Antigen Retrieval Reagent-Basic) is essential for unmasking PECAM1 epitopes . For frozen sections, fixation with 4% paraformaldehyde followed by permeabilization may be required depending on the antibody's epitope accessibility.

Antibody concentration and incubation conditions should be optimized for each tissue type—a concentration of 5 μg/mL with 1-hour room temperature incubation has proven effective for the Human CD31/PECAM-1 Antibody (AF806) in human liver sections . The detection system selection is crucial for sensitivity and specificity—polymer-based detection systems like Anti-Goat IgG VisUCyte HRP Polymer have demonstrated excellent results in visualizing PECAM1 in endothelial cells and sinusoids .

Counterstaining with hematoxylin provides contrast that highlights the DAB-positive PECAM1 staining in vascular structures . Always include both positive controls (tissues with known PECAM1 expression) and negative controls (primary antibody omission or isotype control) to validate staining specificity. For quantitative analysis of vascular density, standardized imaging and analysis protocols should be established to ensure consistency across specimens.

How can PECAM1 antibodies be utilized to investigate endothelial cell barrier function?

PECAM1 antibodies have become instrumental in studying endothelial barrier function through several sophisticated experimental approaches. One validated methodology employs Electric Cell-substrate Impedance Sensing (ECIS) to measure PECAM1-mediated endothelial cell barrier function in real-time . In this approach, endothelial cells are grown to confluence on gold electrodes coated with 50 μg/ml bovine fibrinogen, and barrier function is assessed using an ECIS ZTheta Instrument .

The experimental protocol includes disrupting the endothelial barrier with thrombin (1 unit) and measuring barrier restoration in real-time while manipulating PECAM1 function with domain-specific antibodies . Specifically, adding 40 μg/ml of mAbs such as PECAM-1.2 (targeting Ig Domain 6) or PECAM-1.3 (targeting Ig Domain 1) at the nadir of barrier disruption allows researchers to assess how different PECAM1 domains contribute to barrier recovery .

Data analysis involves calculating the barrier function parameter (Rb), expressed as the average basal electrical resistance (in Ω/cm²) . Statistical analysis using one-way ANOVA followed by Bonferroni's multiple-comparisons test enables rigorous evaluation of how different PECAM1 antibodies affect barrier function . This sophisticated approach has revealed that engagement of membrane-proximal Ig domain 6 can regulate the adhesive properties of PECAM1, with significant implications for controlling endothelial cell migration and barrier function in vascular permeability disorders .

What methodologies can elucidate the role of PECAM1 in endothelial-to-mesenchymal transition?

Investigating PECAM1's role in endothelial-to-mesenchymal transition (EndMT) requires specialized methodologies that combine molecular and cellular approaches. Research has established that CD31/PECAM-1 expression changes are markers of EndMT, making PECAM1 antibodies valuable tools for studying this transition .

A validated experimental approach involves treating Human Microvascular Endothelial Cells (HMVECs) with various factors that induce or inhibit EndMT, followed by Western blot analysis of PECAM1 expression alongside mesenchymal markers . Specifically, researchers have incubated HMVECs with N-FGFR1 in the presence or absence of TGF-β2 for 48 hours, with or without preincubation with AcSDKP (a tetrapeptide that inhibits EndMT) or FGF2 (50 ng/ml) .

The analysis methodology includes Western blotting to simultaneously examine CD31/PECAM-1 levels (as an endothelial marker) alongside mesenchymal markers like SM22α, FSP1, and α-SMA . This approach enables researchers to correlate the loss of PECAM1 expression with the acquisition of mesenchymal markers during EndMT.

Advanced studies have further incorporated siRNA-mediated knockdown of signaling components like FRS2 to dissect the molecular pathways through which PECAM1 expression is regulated during EndMT . This comprehensive methodology has revealed that AcSDKP suppresses TGF-β/smad signaling and EndMT through the FGFR1/FRS2 pathway, demonstrating how modulation of these pathways affects PECAM1 expression and endothelial phenotype maintenance .

How do domain-specific PECAM1 antibodies influence cellular functions differently?

Domain-specific PECAM1 antibodies have proven invaluable for dissecting the functional roles of different PECAM1 regions in cellular processes. Research has demonstrated that antibodies targeting different immunoglobulin-like domains of PECAM1 can have distinct effects on cellular functions, providing insights into domain-specific roles .

A methodological approach for investigating these differential effects involves comparing the impact of antibodies targeting different domains in functional assays. For instance, comparing mAb PECAM-1.3 (specific for IgD1) with mAb PECAM-1.2 (specific for IgD6) in endothelial barrier function or cell migration assays reveals domain-specific contributions to these processes . The experimental protocol includes adding domain-specific antibodies (40 μg/ml) to endothelial cells during recovery from thrombin-induced barrier disruption or following electrical wounding .

Research has shown that engagement of membrane-proximal Ig domain 6 can regulate the adhesive properties of PECAM1, while N-terminal domain 1 is primarily involved in homophilic binding . These differential effects highlight how domain-specific antibodies can be used not only as detection tools but also as functional modulators to probe PECAM1's various roles.

For validation of domain specificity, researchers have used ELISA assays with purified PECAM1 as the target antigen, confirming the domain-specific reactivity of antibody Fab fragments before their use in functional studies . This comprehensive approach enables precise dissection of how different structural regions of PECAM1 contribute to its diverse cellular functions.

What are common challenges when using PECAM1 antibodies and how should they be addressed?

Researchers frequently encounter several challenges when working with PECAM1 antibodies that can affect data quality and interpretation. One common issue is variability in staining intensity across different tissue types due to differences in PECAM1 expression levels and epitope accessibility. To address this, researchers should optimize antibody concentration specifically for each tissue type and application, rather than using a standardized protocol across all specimens.

Another challenge is the potential for non-specific binding, particularly in tissues with high endogenous peroxidase activity or endogenous biotin. Implementing appropriate blocking steps is crucial—use peroxidase blockers before antibody incubation for IHC applications and include a biotin-blocking step when using biotin-streptavidin detection systems. Additionally, including adequate BSA (1-5%) in antibody diluents can reduce background.

Cross-reactivity with related adhesion molecules can complicate interpretation, particularly when studying tissues that express multiple immunoglobulin superfamily members. To address this, validate antibody specificity using PECAM1 knockout controls, as demonstrated with the CD31/PECAM-1 knockout THP-1 human cell line . When knockout controls are unavailable, alternative validation approaches include peptide competition assays or siRNA-mediated knockdown of PECAM1.

Sample preparation challenges include preserving PECAM1 epitopes during fixation and processing. For formalin-fixed tissues, effective antigen retrieval is critical—heat-induced epitope retrieval using basic retrieval reagents has proven successful for PECAM1 detection . For frozen sections, brief fixation (10-15 minutes) with 4% paraformaldehyde typically preserves PECAM1 epitopes while maintaining tissue morphology.

How should contradictory results with different PECAM1 antibodies be interpreted?

When faced with contradictory results using different PECAM1 antibodies, a systematic analytical approach is essential. Contradictions may arise from several factors, including epitope-specific differences, technical variables, or biological complexities. The following methodology helps resolve such discrepancies:

First, analyze the specific epitopes recognized by each antibody. Different PECAM1 antibodies target distinct domains—for example, mAb PECAM-1.3 recognizes N-terminal IgD1, while mAb PECAM-1.2 targets membrane-proximal IgD6 . These domain-specific antibodies may yield different results because certain epitopes might be masked in particular cellular contexts or experimental conditions.

Evaluate how post-translational modifications affect epitope recognition. PECAM1 undergoes glycosylation and phosphorylation that can influence antibody binding. Phosphorylation of cytoplasmic domain epitopes during signaling events may alter the accessibility of C-terminal antibodies like mAb 235.1 .

Consider how experimental conditions affect PECAM1 conformation and epitope exposure. Under reducing conditions in Western blot, PECAM1 typically appears as a 130-140 kDa band, while in Simple Western systems it may appear at 165-186 kDa . These differences reflect how sample preparation impacts protein conformation and epitope accessibility.

When contradictions persist, employ multiple detection methods with the same antibodies. If an antibody yields different results between flow cytometry and immunohistochemistry, this may indicate context-dependent epitope accessibility rather than antibody specificity issues. Ultimately, reconciling contradictory results requires understanding both the technical limitations of each antibody and the biological complexity of PECAM1 expression and function in different experimental systems.

What controls are essential when working with PECAM1 antibodies?

Implementing a comprehensive control strategy is critical for generating reliable data with PECAM1 antibodies. Essential controls include:

• Positive tissue/cell controls: Include samples known to express PECAM1, such as endothelial cells, platelets, or specific leukocyte populations. bEnd.3 mouse endothelioma cell lines serve as excellent positive controls for mouse PECAM1, while Jurkat human acute T cell leukemia cells are suitable for human PECAM1 studies .

• Negative tissue/cell controls: Incorporate PECAM1-deficient samples. The CD31/PECAM-1 knockout THP-1 human cell line provides an ideal negative control for validating antibody specificity . For tissues, use cell types known not to express PECAM1, such as epithelial cells.

• Antibody controls: Include isotype controls matched to the primary antibody's species and immunoglobulin class. For example, when using goat anti-human CD31/PECAM-1 antibodies, include normal goat IgG (AB-108-C) as an isotype control .

• Method-specific controls: For Western blots, include molecular weight markers to confirm the expected 130-140 kDa size of PECAM1 . For IHC and ICC, include a primary antibody omission control and an irrelevant antibody control.

• Application-specific controls: In functional studies, such as those examining barrier function with ECIS, include control antibodies that do not target PECAM1 to confirm that observed effects are PECAM1-specific rather than due to non-specific antibody binding or Fc receptor engagement .

• Domain-specificity controls: When using domain-specific antibodies, validate their reactivity using ELISA with purified PECAM1 as the target antigen . This confirms that the antibodies recognize the intended epitopes before their application in functional studies.

Implementing this comprehensive control strategy enables confident interpretation of experimental results and identification of any technical artifacts or biological variations.

How are PECAM1 antibodies contributing to research on blood-brain barrier disruption?

PECAM1 antibodies have become instrumental in advancing our understanding of blood-brain barrier (BBB) disruption in neurovascular pathologies. Recent research has employed PECAM1 antibodies to investigate the relationship between neutrophil infiltration and BBB integrity following stroke .

A sophisticated methodological approach involves using PECAM1 antibodies in conjunction with IgG extravasation assays to quantify BBB breakdown in experimental stroke models . Specifically, researchers have examined how neutrophil depletion (using anti-Ly6G antibodies) affects BBB integrity and neovascularization after stroke, using PECAM1 antibodies to visualize the vascular network .

Confocal imaging of IgG extravascular deposits in the peri-infarct cortex at 14 days post-stroke, combined with quantitative analysis, has revealed that neutrophil depletion significantly reduces BBB breakdown . This methodological approach enables researchers to correlate vascular integrity (visualized with PECAM1 antibodies) with BBB function (assessed by IgG extravasation).

Statistical analysis using one-way ANOVA has demonstrated significant differences between sham-operated mice and those treated with control antibody (P < 0.0001), as well as between control antibody-treated and anti-Ly6G antibody-treated mice (P = 0.0041) . These findings highlight how PECAM1 antibodies contribute to our understanding of the cellular mechanisms underlying BBB dysfunction in neurological disorders, potentially informing therapeutic strategies targeting vascular integrity in stroke and other neurovascular diseases.

What advances have been made in using PECAM1 antibodies with nanodisk technology?

Innovative research has combined PECAM1 antibodies with nanodisk technology to create powerful tools for studying PECAM1 function in controlled membrane environments. This approach involves incorporating PECAM1 into nanodiscs—disc-shaped phospholipid bilayers encircled by membrane scaffold proteins—which maintain the protein in a native-like membrane environment while enabling precise manipulation and analysis .

The methodology begins with generating PECAM1-containing nanodiscs (Pnanos) that preserve both the extracellular and cytoplasmic domains of the receptor. Validation of these constructs involves immobilizing the nanodiscs in microtiter wells and evaluating their recognition by a series of domain-specific antibodies, including mAbs that recognize N-terminal IgD1 (PECAM-1.3), membrane-proximal IgD6 (PECAM-1.2), and the cytoplasmic domain (235.1) .

ELISA analysis has confirmed that these antibodies strongly recognize PECAM1 in the nanodisc format, indicating that both extracellular and cytoplasmic domains remain accessible . Further validation through FACS analysis and immunofluorescence microscopy has demonstrated that Pnanos, but not empty nanodiscs (Enanos), bind to PECAM1-expressing cells, confirming the functionality of the PECAM1 incorporated into the nanodiscs .

This innovative approach enables researchers to study PECAM1 in a controlled membrane environment, facilitating investigations into how membrane context influences PECAM1 function and how antibodies targeting different domains affect receptor behavior. The nanodisc technology provides a valuable platform for dissecting the structural and functional relationships of PECAM1 domains, potentially enabling the development of domain-specific therapeutic strategies for vascular disorders involving PECAM1 dysfunction.